The present invention relates to the field of pipes made by assembling together steel pipe elements, each having an internal lining of plastics material protecting the steel walls of said pipe from corrosion.
The present invention relates more particularly to a device and a method for installing a tubular junction sleeve made of plastics material for assembling a pipe from said unitary pipe elements and for performing electro-fusion, said sleeve being pressed against and secured to said lining by electro-fusion by the Joule effect at the junction between the abutting ends of two unitary pipe elements, as described in particular in WO 2012/017171.
More particularly, the present invention relates to pipes for conveying corrosive fluids, in particular undersea pipes conveying sea water under pressure for injection into wells in oil fields, and still more particularly connection pipes resting on the sea bottom or bottom-to-surface connection pipes.
The present invention relates more particularly to connecting together two internally-lined unit pipe elements, and more particularly elements presenting a length of 24 meters (m) or 48 m that are installed in oil fields in deep water, e.g. in depths of 2000 m to 3000 m, or even more, from a laying ship fitted with J-lay towers.
In known manner, the ends of said pipe elements are assembled together end to end by welding, and the internal lining inside said pipe elements comes to an end at a significant distance from each end of said pipe elements, e.g. a distance of 100 millimeters (mm) to 300 mm, so that the heating of the steel wall while the ends are being welded together does not damage said lining. There is then a problem of how to protect against corrosion the non-lined zone extending between the end of the lining of pipe element No. N and the end of the lining in the following pipe element No. N+1.
Patent WO 2006/042925 in the name of the Applicant discloses such an assembly of pipes provided with internal linings. The internal lining method is known as “swagelining”.
The terms “liner” or “internal lining” as used herein correspond to an internal covering commonly known as a “liner”.
In WO 2012/017171, the Applicant describes an improved way of assembling together two pipe elements made of steel coated with internal lining by using a tubular junction sleeve, which method is both mechanically more reliable in terms of sealing while also being simple and inexpensive to perform, in particular when assembly is performed on site by a ship at sea, using pipe elements of short length that are suitable for laying from a ship at sea.
To do this, the tubular junction sleeve is interposed between two pipe elements made of steel with internal lining made of thermoplastic material that are assembled together end to end, the ends of the two pipe elements being welded together. Said tubular junction sleeve made of thermoplastic material, preferably of material identical to that of said lining, is inserted inside the pipe at the abutting ends of the two pipe elements, so that the terminal portions at the ends of said sleeve are at least partially in leaktight contact with respective terminal portions at the ends of said internal lining of the two pipe elements. Said tubular junction sleeve presents a Joule-effect heater wire at each of said terminal portions of the sleeve at said zone for leaktight contact with the terminal portions of said linings, which wire is on the outer surface of each of said terminal portions at the ends of said sleeve, and is preferably arranged as a spiral. Said zone of leaktight contact is a zone of welding by fusion between the materials constituting each said terminal portion of the sleeve and each said terminal portion of said lining where they come into with each other and where said heater wire passes.
It is important for the contact between the sleeve and the liner to be leaktight in order to avoid any sea water making contact with the welding zone facing said tubular sleeve. In the event of water penetrating between the sleeve and the pipe, and when the pipe is a water injection pipe, such direct contact could lead to electrochemical corrosion phenomena of the steel pipe and of the weld, assuming that said mechanical connection between the sleeve and the lining is not necessarily leaktight.
It can be understood that said fusion zone is obtained by electrically powering said Joule effect heater wire creating heating at the interface between said contacting surfaces of the terminal portions of the sleeve and of the lining. Said fusion-welding zone (referred to below as “fusion zone” for short) is thus performed in this example by the so-called “electro-fusion” method that makes it possible to provide a zone of leaktight contact that is particularly reliable and strong.
Said heater wire is applied on an outer surface of a terminal portion of the sleeve with one end of the heater wire reaching the inner surface of said sleeve at an electrical connector making it easier to electrically power the heater wire from inside the pipe while assembling the pipe, as explained below.
Said sleeve may be prefabricated with a said heater wire already applied to its surface, which is easier to perform than applying a heater wire in situ inside said pipe elements on the surfaces of said internal linings of the in situ pipe element inside the pipe before inserting said sleeve inside said pipe element.
In another implementation, the heater wire is not applied as a spiral, i.e. it is not made as a plurality of turns arranged in succession in the direction of their axis of revolution in order to cover said fusion zone, but said wire makes at least one turn around said axis of revolution around the fusion zone while performing a plurality of go-and-return paths between the two ends of said fusion zone in the axial direction of the axis of revolution of said fusion zone.
A method of making a pipe with such a sleeve comprises assembling together pipe elements, each including a said sleeve with a terminal portion of smaller thickness at each end, and a respective said tubular junction sleeve inserted into only one end of each said pipe element and projecting therefrom, the projection of said sleeve defining a male end of each said pipe element suitable for being connected to an end that does not have a said sleeve and that defines a female end of another said pipe element of the same kind. For this assembly, the following steps are performed:
1) said female end that does not have a tubular junction sleeve of a pipe element is then engaged by force around the male end of the stationary tubular junction sleeve that projects axially from the other pipe element in the longitudinal direction (XX′) until said terminal portion of the sleeve of said male end of said terminal pipe element is in contact with said terminal portion of the lining of said female end of said pipe element for assembly, each said sleeve including on each of said terminal portions of the sleeve a said Joule effect heater wire wound in a double spiral; then
2) electrically powering said heater wire of said terminal portion, preferably while simultaneously exerting pressure between said contacting sleeve terminal portion and said lining terminal portion in order to provide a said zone for welding by electro-fusion in at least a portion of the interface at the surfaces of each said sleeve terminal portion and each said lining terminal portion in mutual contact and having the heater wire double spiral running thereover at the surface of the sleeve in order to provide a said zone of leaktight contact by fusion; and
3) welding together of the ends of the two abutting pipe elements at their outer peripheries.
In WO 2012/017171, said pressure is exerted against the inner surface of the sleeve via its said terminal portion by inserting inside the sleeve a device that includes an inflatable cell, which cell is initially deflated at least in part, said cell including or co-operating at its surface with an electrical power supply connector that is positioned in such a manner that, when said cell is inflated, said electrical connector of the cell can co-operate with the electrical connector on the inner surface of the sleeve including the terminals of the heater wire, and then said cell is inflated.
More precisely, in WO 2012/017171, and with reference to FIGS. 9A-9E, an expandable mandrel 20 is used that enables electro-fusion to be performed at the junction between the tubular sleeve 3 and the internal lining 2 via the surface of revolution 2a. The mandrel 20 has a rigid core 21 in the form of a wheel rim, an expandable membrane in the form of an air chamber 22 that can be inflated by means of an umbilical 23 fed with compressed air, said umbilical also delivering electrical power to a power supply connector 20a. The mandrel 20 is thus inserted inside the tubular junction sleeve 3 so as to position the connector 20a facing the complementary connector 7 of said tubular junction sleeve. The mandrel is then inflated and electricity is injected so as to melt said zone covered by the heater wire. Expansion of the mandrel serves to guarantee compactness in the fusion plane, and also to guarantee the absence of bubbles of air, where such bubbles would be harmful to good sealing in the melted surface.
Furthermore, said mandrel does not enable said junction sleeve to be inserted and installed prior to welding by electro-fusion, with the operations of installing the sleeve being difficult to perform.